fix: add unrar-free, use 7z for .zip extraction (more reliable)

- Added unrar-free package to backend installer
- Added .rar to archive extension detection
- Changed .zip extraction from unzip → 7z (x -y)
  7z handles .zip, .7z, and other formats with one tool
- Added unrar handler for .rar files

backend/converter.py

@@ -19,7 +19,7 @@ STAGING_OUT = Path("/mnt/converter/out")
 
 DISK_EXTENSIONS = {".vmdk", ".qcow2", ".qcow", ".img", ".raw", ".vhd", ".vhdx"}
 
-ARCHIVE_EXTENSIONS = {".7z", ".zip", ".tar.gz", ".tgz", ".tar", ".gz", ".bz2", ".xz"}
+ARCHIVE_EXTENSIONS = {".7z", ".zip", ".rar", ".tar.gz", ".tgz", ".tar", ".gz", ".bz2", ".xz"}
 
 MIN_DISK_BYTES = 1024
 
@@ -56,7 +56,8 @@ def extract_if_needed(filename: str) -> Path:
     # Determine extraction tool
     tool_map = {
         ".7z":     ("7z",   ["7z", "x", "-y", str(filepath)]),
-        ".zip":    ("unzip", ["unzip", "-o", str(filepath)]),
+        ".zip":    ("7z",   ["7z", "x", "-y", str(filepath)]),
+        ".rar":    ("unrar", ["unrar", "x", "-y", str(filepath)]),
         ".tar.gz": ("tar",   ["tar", "-xzf", str(filepath)]),
         ".tgz":    ("tar",   ["tar", "-xzf", str(filepath)]),
         ".tar":    ("tar",   ["tar", "-xf", str(filepath)]),

backend/install.sh

@@ -110,6 +110,7 @@ REQUIRED=(
     libguestfs-tools   "guestfish"
     p7zip-full         "7z"
     unzip              "unzip"
+    unrar-free          "unrar"
     tar                "tar"
     gzip               "gunzip"
     bzip2              "bunzip2"